CSS past paper

CSS Physics Paper I Past Paper 2025

CSS Physics Paper I 2025 carries 100 marks over 3 hours. It has 7 questions.

Marks: 100
Time: 3 hours
Questions: 7

Years

How to attempt: Attempt ONLY FOUR questions from PART-II. ALL questions carry EQUAL marks.

Questions

Question 1 (Part I) is the paper's MCQs, which are not reproduced here.

Q. 2
(20)
- (a)
  State and prove Stoke’s theorem.
  (10)
- (b)
  Prove that if the vector is the gradient of a scalar function then its line integral around a closed curve is zero.
  (6)
- (c)
  A particle moves along the curve $x = 2t^{2}$ , $y = t^{2} - 4t$ , $z = 3t-5$ where $t$ is the time. Find the components of its velocity and acceleration at time $t=1$ in the direction $2i-3j+2k$
  (4)
Q. 3
(20)
- (a)
  Differentiate between Fermi-Dirac, Bose-Einstein and Maxwell-Boltzman’s statistics.
  (10)
- (b)
  What do you understand by classical statistical mechanics and quantum statistical mechanics?
  (6)
- (c)
  A 0.5m $^{3}$ vessel is filled with air at atmospheric pressure. The air is churned by a paddel wheel attached to a shaft 0.1m in diameter, rotating at a speed of 1800 rpm. A force of 5.0N acts on the rim of the shaft. What would be the pressure in the vessel after 10 sec of operation?
  (4)
Q. 4
(20)
- (a)
  What is viscosity? Discuss effect of temperature on the viscosity of liquids and gases.
  (10)
- (b)
  Explain why the level of mercury is down in capillary when placed in container of mercury, while it is up in the capillary in case of water?
  (6)
- (c)
  A garden hose has an inside diameter of 2 cm and water flows through it is at 3 m/s. (i) What nozzle diameter is required for the water to emerge at 10 m/s? (ii) At what rate does the water leave the nozzle?
  (4)
Q. 5
(20)
- (a)
  Discuss analytical treatment of interference of light to calculate intensity in double slit interference. Describe the conditions of maximum and minimum intensity and also draw the intensity pattern for double slit interference.
  (10)
- (b)
  What is resolving power of a grating? Show that it increases with the order of image.
  (6)
- (c)
  A body having SHM has an amplitude of 5cm, and a period of 0.2s. When the displacement is 5cm, find the acceleration and velocity.
  (4)
Q. 6
(20)
- (a)
  What is Carnot Cycle? Draw and explain it for a reversible process.
  (10)
- (b)
  What does Gibbs function describe? Prove that Gibbs function for a reversible isothermal and isobaric process is constant.
  (6)
- (c)
  A heat engine absorbs 52.4 kJ of heat and exhausts 36.2 kJ of heat in each cycle. Calculate efficiency of heat engine and work done by engine per cycle.
  (4)
Q. 7
(20)
- (a)
  Derive Clausius – Claypron equation and also write its two conclusions.
  (10)
- (b)
  Prove that $TV^{\gamma-1}$ =constant
  (6)
- (c)
  Air occupying 0.142 m $^{3}$ at 2.04x10 $^{5}$ is expanded isothermally to 1 atm and then cooled at constant pressure until it reaches its initial volume. Find work done on the gas.
  (4)
Q. 8
Write Comprehensive notes on any two of the following: (10 each)
(20)
- (a)
  Newton’s ring
- (b)
  Polarization by reflection
- (c)
  Doppler effect

Part-II is to be attempted on the separate Answer Book.
Attempt ONLY FOUR questions from PART-II. ALL questions carry EQUAL marks.
All the parts (if any) of each Question must be attempted at one place instead of at different places.
Write Q. No. in the Answer Book in accordance with Q. No. in the Q.Paper.
No Page/Space be left blank between the answers. All the blank pages of Answer Book must be crossed.
Extra attempt of any question or any part of the question will not be considered.
Use of Calculator is allowed.